Size matters

[Jim Yergin]

I've had my '41 Plymouth wagon back on the road for about five years now. When I got it together I checked the operation of the tail lights, the brake lights and the turn signals and they all worked. However, until recently, I had never checked the brake lights and the turn signals with the tail lights on. When I did the other day, I discovered that there was no noticable difference in the brightness of the lights when the brakes were applied or the turn signals were on. What I discovered is that the wires to the brake/turn signal lights were undersized, probably 14 gauge. I ran new 12 gauge wires and the lights are now noticeably brighter when the brakes or turn signals are on.

Jim Yergin

[greg g]

Jim, you might also want to check your ground paths.  With a lot of restorations, when you reassemble things you get a lot of metal to paint contact rather than metal to metal. You might try a jumper wire from a lamp to a known good ground and see if the brightness improves even more.  Are your lamps mounted to the wood of the body?  They probably have a dedicated grounding wire if they are, but is that wire getting a good clean path to the chassis?

[Jim Yergin]

Greg,

The first thing I did was check and clean my grounds. Because the tail lights are mounted to the wooden tailgate, they each have dedicated ground wires that run to the chassis.

Jim Yergin

[desoto1939]

JIm the 14 gage wire should have had enought pwer to supply the juice to light the brake lights.  As stated above I would run a ground wire off the inside of the taillight bucket to a good ground on the frame to see if that make the lights brighter.  I had a similar situation after my repaint job and also found that a new grounding wire helped solve my light problem.  Also can you spray the inside of the taillight bucket with some chrome paint this will also provide fsome reflective background to your buckets.  I also did this.  just mask over the tiallight socket so no paint gets into the socket.

 

Rich HArtung

[Jim Yergin]

Rich,

I appreciate your suggestions but the lights are working properly now.

As I stated in my reply to Greg, I have clean dedicated ground wires from each light unit to the chassis frame. For what ever reason, the undersized wires were not supplying adequate power and the new heavier gauge wires do.

Jim Yergin

[Young Ed]

Rich,

I appreciate your suggestions but the lights are working properly now.

As I stated in my reply to Greg, I have clean dedicated ground wires from each light unit to the chassis frame. For what ever reason, the undersized wires were not supplying adequate power and the new heavier gauge wires do.

Jim Yergin

 

Part of what Rich is saying is that the 14g should have been enough. OEM spec is 16g. I rewired mine using all 14g or better though. So possibly those wires were corroded inside or had a bad connection that was fixed when you replaced the wires.

[desoto1939]

I discovered that when i did some rewiring and took apart the old wire harness they had used steel wire and not coper wire.  So the steel wire was getting some corrosion build up in the old style cloth covering becasue the moisture was getting into the old wires.  The new cloth covered wire that you get from Rhode Island wire stillhas the plastic covered wire which is copper and then the cloth is pulled over the plastic. So you are now getting modern wire      with plastic protection adn the look of old style wiring coloring.

 

So the New stuff is better than NOS wire.  Use the NOS wire as a guide to make your own loom. That is what these      companies are doing that make the new harnessess.

 

Glad you solved the issue.  In our older cars is is better to go with a heavier wire.  I also did 14 and 12 gage wiring.

 

Rich HArtung

Desoto1939@aol.com

[Jim Yergin]

I see now that my guess that the original wire size was 14 gauge was just that, a guess. It could very well have been 16 gauge.

I agree it could also have been a defect in the wiring. The important thing is that it is now fixed and the cars behind me have a better shot at seeing my brake lights and turn signals.
Jim Yergin

Edited September 23, 2013 by Jim Yergin